Another recent problem among many for my car. Anyway, yesterday I dropped my little sister off at school, and not even a 1/4 mile away is an intersection which I was sitting at. My SES light came on, and it always comes on (Don't have a code reader), but only during peak temperatures. I saw my temp indicator was past the 3/4 mark and on it's way to the red zone. I pulled over, let it cool, and got home. For the remainder of the day I used my dad's truck. I checked under my car and all around the engine bay for some kind of leak, although it might have evaporated since it was hot. All the hoses are in good condition. My radiator fan is working, and nothing is cracked or damaged (That I can see). Once the engine got hot, the temp indicator would go half way, then drop a little bit and show an SES light, and it would hold somewhat steady. This morning I took it to autozone, they read codes but couldn't help me with my overheating issue. When I started my car to leave, I don't know why, I just turned on the AC. As soon, and I mean right after, the AC turned on the temp reading shot down to the first mark, 1/4. So I'm thinking I have a bad thermostat.

*Sorry for long post, but I wanted to give as much information and detail. Also, the codes were 35 and 49, 35 being a faulty IAC, and 49 was a vacuum leak. I'm not sure if these readings are accurate and I'm not sure if they're related. Thanks for reading.

*EDIT* Ok also the other thing is that the times that I had the overheating issue I did NOT have the AC on.

Last edited by RedVision_350; 08-31-2007 at 10:12 AM..
Reason: More info.

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It could be a bad thermostat, if turning on the A/C (which turns on the fan) brought the temps down that much. This time of year it's not uncommon for the temperature gage to get up to 3/4 in slow traffic, even just sitting through 2 cycles at a signal I've noticed my temperature gage creep up pretty quickly. I don't think the fan even comes on until the temp is about 3/4 anyway, you may have been sitting at the stop light and saw the temperature gage rise and shut off the engine before the fan had a chance to kick in. Once the fan comes on it should stay on until the temperature falls below half.

I've seen more thermostats stuck open than stuck closed (I think they are designed to be fail-safe) a thermostat stuck open won't cause your vehicle to overheat, and it will let the engine temperature drop lower than the optimal operating temperature with sufficent air flow, do you notice your heater doesn't feel very warm on cold mornings? Are you certain your fan works? Does it come on when the engine is hot and the A/C is off?

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Another recent problem among many for my car. Anyway, yesterday I dropped my little sister off at school, and not even a 1/4 mile away is an intersection which I was sitting at. My SES light came on, and it always comes on (Don't have a code reader), but only during peak temperatures. I saw my temp indicator was past the 3/4 mark and on it's way to the red zone. I pulled over, let it cool, and got home. For the remainder of the day I used my dad's truck. I checked under my car and all around the engine bay for some kind of leak, although it might have evaporated since it was hot. All the hoses are in good condition. My radiator fan is working, and nothing is cracked or damaged (That I can see). Once the engine got hot, the temp indicator would go half way, then drop a little bit and show an SES light, and it would hold somewhat steady. This morning I took it to autozone, they read codes but couldn't help me with my overheating issue. When I started my car to leave, I don't know why, I just turned on the AC. As soon, and I mean right after, the AC turned on the temp reading shot down to the first mark, 1/4. So I'm thinking I have a bad thermostat.

*Sorry for long post, but I wanted to give as much information and detail. Also, the codes were 35 and 49, 35 being a faulty IAC, and 49 was a vacuum leak. I'm not sure if these readings are accurate and I'm not sure if they're related. Thanks for reading.

*EDIT* Ok also the other thing is that the times that I had the overheating issue I did NOT have the AC on.

the Code 35 could be causing code 49 and might be helped by a good cleaning of your throttlebody and IAC valve.....it could just be that you are panicking at seeing the needle going that far......what other symptoms are you getting that lead you to believe the car is overheating? What part of the country do you live in? It's not uncommon for the car to heat up while sitting like that.....but you probably turned the AC on right before the computer kicked the fan on anyway...which it is designed to do......

...The streets will flow with the blood of all the non-believers!!!! And all those who won't include their vehicles vital information in their posts!!!!

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